The proposed research is a continuing effort to investigate patho- physiologic mechanisms responsible for the hypoglycemia in the neonatal and childhood periods. During the past two years the emphasis of this work has been on studying substrate and hormonal levels, in particular, glucose, amino acids, ketone bodies, lactate, pyruvate, insulin, growth hormone and glucagon prior to and during hypoglycemia in children and infants known to be at risk for hypoglycemia (i.e. ketotic hypoglycemia, hypopituitarism and the small for gestational age infant). A clearer understanding as to the factors involved in the etiology of these various forms of hypoglycemia has been derived from these studies.